1. Field of the Invention
The invention relates in general to a charge pump, and more particularly to a charge pump capable of reducing the number of external capacitors and an electronic device using the same.
2. Description of the Related Art
With rapid advance in technology, charge pumps have been provided and widely used in various applications. For example, a charge pump can be used as a power circuit of an integrated circuit (IC). In general, the charge pump includes multiple switches, and two external capacitors (such as flying capacitors) disposed outside the IC. The multiple switches are switched in order. In a first operating period, a first external capacitor is discharged to stabilize the output voltage, and a second external capacitor is charged to generate a cross-voltage. In a second operating period, the voltage level at one terminal of the second external capacitor is boosted or stepped down, and the other terminal of the second external capacitor is discharged to the first external capacitor, so that the first external capacitor is charged, resulting in a boosted or reduced output voltage at the other terminal of the second external capacitor.
However, the existing charge pump normally requires an external capacitor with higher capacitance (such as tens of microfarads (uf)), and is thus disadvantaged by having circuit area and higher manufacturing cost. Therefore, how to provide a charge pump with smaller circuit area and lower manufacturing cost has become an imminent task for the industries.